At scenes of disaster management, when a disaster occurs, it is important to instantaneously catch a disaster occurrence place. However, it is difficult to set a physical sensor that catches a disaster event in every single place where there is a risk of occurrence of a disaster. Thus, it is examined to use disaster witness reports through social media as “sensors by human”. The social media in this connection is media used by users for positing and exchanging messages on line and thereby performing information distribution. Examples of social media include Twitter (a registered trademark of Twitter, Inc.), Facebook (a registered trademark of Facebook, Inc.), and the like. For example, there is a technique in which a message related to a disaster is extracted from social media to extract information related to a disaster occurrence place.
Related art is described in, for example, Japanese Laid-open Patent Publication No. 2014-6735, Japanese Laid-open Patent Publication No. 2013-50919, and Japanese Laid-open Patent Publication No. 2013-235527.